One example of the above-noted self-propelling work vehicle is a zero-radius-turning mower (ZRTM).
The ZRTM known from U.S. Pat. No. 7,748,480 includes drive wheels driven by an engine, a mower unit and a control system. The control system has right and left control handles provided to permit control of mower speed and direction from the operator station. Each control handle is pivotally coupled to a chassis for pivotal movement about a transverse pivot axis to be pivotable from a first or neutral position in either a first direction or a second direction. Each control handle has an arm forming a pivot joint for receiving an end of the attachment member such that the attachment member and arm may pivot about a handle pivot axis contained within a vertical plane that is orthogonal to the transverse pivot axis. The pivot joint permits movement of the handles inwardly and outwardly to better accommodate operator ingress/egress.
U.S. Pat. No. 7,458,432 discloses a dual lever steering control mechanism for mounting a control lever to a mower. The dual lever steering control mechanism includes a housing, a forward/reverse lever, and a neutral position lever pivotably attached to the forward/reverse lever. The housing defines an opening for receiving the forward/reverse lever to be pivotable about a first pivot axis, and a slot for allowing the neutral position lever to be pivotable about a second pivot axis that is orthogonal to the first pivot axis. Further, a safety switch is provided for detecting entry of the neutral position lever into the slot in parking the vehicle. The neutral position lever and the control lever gripped by the operator are connected to each other to be positionally adjustable through a bolt and a plurality of slots.
While the positional relationship between the control lever and the neutral position lever is adjustable in the above mechanism, no particular consideration is given to the positional adjustment between the opening and the slot defined in the housing.
In the above-noted conventional art, it is difficult to precisely adjust the position of the guide unit defining the opening and slot for allowing shift movement in two directions of the handle levers, to the shifting positions of the handle levers. If those control levers are used for controlling a variable propelling power supply section for supplying forward drive power and reverse drive power to the drive wheels, it is required to precisely adjust the positional relationship noted above because an upper limit for the first shift movement determines a maximum forward speed.